Fine particle of perovskite oxide, particle having deposited perovskite oxide, catalyst material, catalyst material for oxygen reduction, catalyst material for fuel cell, and electrode for fuel cell

Abstract

A catalyst for electrodes in solid-polymer fuel cells which comprises metal oxide particles themselves. The catalyst contains fine transition-metal oxide particles having, in the main phase, a perovskite structure represented by the general formula ABO 3 (wherein A represents one or more elements selected among lanthanum, strontium, cerium, calcium, yttrium, erbium, praseodymium, neodymium, samarium, europium, silicon, magnesium, barium, niobium, lead, bismuth, and antimony; and B represents one or more elements selected among iron, cobalt, manganese, copper, titanium, chromium, nickel, and molybdenum), the fine oxide particles having lattice constants satisfying the following relationship (1): 1.402<2 b /( a+c )<1.422  (1) wherein a and c represent the minor-axis lengths of the perovskite type crystal lattice and b represents the major-axis length thereof.

1. Fine transition metal oxide particles comprising, as main phase, a perovskite type structure as represented by the general formula ABO 3 , 
       (where “A” denotes one or more elements selected from the group of lanthanum, strontium, cerium, calcium, yttrium, erbium, praseodymium, neodymium, samarium, europium, silicon, magnesium, barium, niobium, lead, bismuth, and antimony, “B” denotes one or more elements selected from the group of iron, cobalt, manganese, copper, titanium, chrome, nickel, and molybdenum) wherein the lattice constants of said fine oxide particles meet the following conditional equation (1):
   1.402<2 b /( a+c )<1.422  (1)
 
 
       (where, “a” and “c” denote the minor-axis lengths of the perovskite type crystal while “b” denotes its major-axis length), and wherein said fine oxide particles contain a noble metal. 
     
     
       2. Fine perovskite type oxide particles as claimed in  claim 1  comprising mainly iron as the element denoted by “B” (B-element). 
     
     
       3. Fine perovskite type oxide particles as claimed in  claim 1  wherein the average particle diameter is 1 to 20 nm. 
     
     
       4. Fine perovskite type oxide particles as claimed in  claim 1  wherein said noble metal is in the form of noble metal atoms substituted for part of the atoms constituting the oxide crystal lattice, or in the form of noble metal crystals combined with oxide crystals to form composite structures, or in the form of noble metal particles adhered to the oxide surface. 
     
     
       5. Fine perovskite type oxide particles as claimed in  claim 1  wherein the element ratio of said noble metal to the total quantity of said B-element is in the range of 1 to 20%. 
     
     
       6. Perovskite type oxide-supporting particles comprising fine perovskite type oxide particles as claimed in any one of  claims 1 ,  2 ,  3 ,  4  and  5  supported on an electrically conductive carrier. 
     
     
       7. Perovskite type oxide-supporting particles as claimed in  claim 6  wherein said electrically conductive carrier is electrically conductive carbon particles. 
     
     
       8. Perovskite type oxide-supporting particles as claimed in  claim 6  wherein the ratio by weight of the supported fine perovskite type oxide particles in the perovskite type oxide-supporting particles ([weight of fine perovskite type oxide particles]/[total weight of oxide-supporting particles]) is in the range of 5 to 50 wt %. 
     
     
       9. A catalyst material comprising, as a primary component, fine perovskite type oxide particles as claimed in any one of  claims 1 ,  2 ,  3 ,  4  and  5 . 
     
     
       10. A catalyst material for oxygen reduction comprising, as a primary component, fine perovskite type oxide particles as claimed in any one of  claims 1 ,  2 ,  3 ,  4  and  5 . 
     
     
       11. A catalyst material for fuel cells that uses the oxygen reduction action of the catalyst material for oxygen reduction claimed in  claim 10 . 
     
     
       12. An electrode for fuel cells comprising a catalyst material for fuel cells as claimed in  claim 11 .